1. Field of the Invention
The invention relates to a backlight module and, more particularly, to a backlight module capable of fixing an optical film assembly effectively and a display device utilizing the same.
2. Description of the Prior Art
Since a liquid crystal display (LCD) has advantages of thin thickness, light weight, low power consumption, no radiation pollution, and being compatible with semiconductor process, it has been applied in various electronic devices including notebook, mobile phone, digital still camera, personal digital assistant, and so on. The LCD utilizes a backlight module to provide light for a display panel so as to display images. In general, an optical film assembly is disposed in the backlight module and used to improve optical characteristics of light. The optical film assembly may comprise lots of optical films including a prism film, a diffusing film, and so on.
Referring to FIGS. 1 and 2, FIG. 1 is a partial schematic diagram illustrating a backlight module 10 of the prior art, and FIG. 2 is a partial schematic diagram illustrating a backlight module 20 of the prior art. As the backlight module 10 shown in FIG. 1, a protruding portion 102 of an optical film assembly 100 is hung on a bending portion 122 of a back cover 120. As the backlight module 20 shown in FIG. 2, a protruding portion 202 of an optical film assembly 200 is hung on a protuberance 222 of a plastic frame 220. Therefore, when a large size display device equipped with the backlight module 10 or 20 stands or faces down, the optical film assembly 100 or 200 will not fall off a frame of the backlight module 10 or 20. Furthermore, some prior arts embed cupper pillar in a back cover to hang an optical film assembly.
However, the aforesaid structures for fixing the optical film assembly always have a specific thickness (at least more than one millimeter), so they may occupy much space in the display device. In addition, most of the back covers are made of metal. If there are bending portions bended from the back cover, not only the span between the bending portions cannot be controlled easily but also the deckle edges of the bending portions may cut off the optical film due to vibration or collision. Moreover, there is always a gap between the bending portion and the frame, so dust may enter the backlight module through the gap. On the other hand, if the optical film assembly is fixed by the protuberance of the plastic frame, the plastic frame has to be designed in relation to the back cover. The plastic frame usually consists of an upper frame and a lower frame, such that the amount of molds increases and then the manufacturing cost increase correspondingly. As to the fixing manner of embedding cupper pillar, it will raise the cost of parts and expend large working hours and the optical film may be cut off due to single contact force.